Optical devices that include waveguides for guiding light signals are employed in a variety of industries such as telecommunications. It is often desirable to transfer a light signal carried by a waveguide in one of these devices to a waveguide on another one of these devices. This transfer can be performed by allowing the light signal to travel through free space between devices. For instance, a first waveguides on a first device can terminate at a first port that directs light signals carried in the first waveguide device in a direction toward a location above the device. A second waveguide on the second device can also terminate at a second port configured to receive light signals traveling toward the second device. As a result, the second device can be positioned over the first device so the second port receives light signals that exit the first port on the first device. During operation of the devices, a light signal guided along the first waveguide exits the first device through the first port and travels between the first port and the second port. The light signal is then received at the second port and is then guided along the second waveguide.
The transfer of the light signal between the devices can require precise alignment between the ports on the different devices. Many devices include alignment openings that are used to achieve this alignment. The alignment openings on a device generally extend into a surface of the device. When the devices are aligned, an alignment structure such as a ball is positioned so it spans an alignment opening in each of the devices. For instance, using the above example, an alignment structure such as a ball can span the distance between an alignment opening on the first device and an alignment opening on the second device.
These alignment openings are etched into the devices. Because of non-uniformity in the etching processes, the depth of the alignment openings on different devices is often inconsistent. The depth of these alignment openings can determine the separation between two devices. As a result, the non-uniform depth of these openings can cause inconsistent separation between different pairs of devices. However, the transfer of light signals between the devices is often most efficient when the devices are at a particular separation. As a result, the inconsistent separation of different devices is a source of optical loss in the system.
For the above reasons, there is a need for improved transfer of light signals between optical devices.